1. Field of the Invention
The present invention relates to a recording/reproducing separated type magnetic head for use in magnetic recording disk drives and, in particular, it relates to a thin film recording head having a narrow track width used at high density recording and high track pitch.
2. Description of Related Art
In recent years, along with the improvement in the recording density in magnetic recording disk drives, there has been a strong demand for the improvement in the performance of recording media, as well as the development of thin film magnetic head excellent in recording/reproducing characteristics. At present, heads using MR (Magnetic Resistive Effect) elements or GMR(Giant Magnetic Resistive Effect) elements capable of obtaining high read output are used as the recording head. Further, TMR (Tunnel Magnetic Resistance) elements capable of obtaining further higher reproducing sensitivity have also been developed. On the other hand, existent induction type thin film recording heads utilizing electromagnetic induction are used for the recording head, and recording/reproducing separated type thin film magnetic heads in which the recording head and the wiring head are formed integrally as described above are used.
To improve the recording characteristics of the thin film recording head, it is necessary to generate strong and sharp recording magnetic fields for effective recording to recording media at high coercivity. However, magnetic saturation is caused in the magnetic pole front end of the thin film recording head due to decrease of the track width along with the improvement in the track density, resulting in a problem of lowering the recording magnetic fields. Further, there is a problem that the recording magnetic fields should leak beyond the track width to adjacent track portions.
An existent thin film magnetic head has a structure as described in FIG. 2 of the Patent Document 1, in which an upper magnetic pole is separated into an upper magnetic pole front end layer and an upper magnetic pole upper layer. In this structure, as shown in FIG. 3, a lower magnetic shield 2 made of a soft magnetic material for improving resolution upon reproducing and eliminating the effects of external magnetic fields is disposed on a substrate 1 made of a non-magnetic material, a reproducing gap 3 made of a non-magnetic insulative material is disposed on the lower magnetic shield 2, and a reproducing element 4 comprising an MR or GMR element is disposed in the reproducing gap 3. A lower magnetic pole 5 made of a soft magnetic material used also as an upper magnetic shield is disposed on the reproducing gap 3 and, further, a recording gap layer 6 is disposed. A depth defining non-magnetic layer 7 for defining the gap depth is disposed on the gap layer 6 and, further, an upper magnetic pole front end layer 8 and an upper magnetic layer rear end layer 9 are disposed and a gap therebetween is filled and planarized with a non-magnetic insulating layer 10. A coil insulating layer 11 is disposed on the surface planarized, and lower conductor coils 12 and upper conductor coils 12′ are disposed in the coil insulating layer 11. The conductor coils may sometimes consist of only one layer. Further, an upper magnetic pole upper layer 13 is disposed and the entire head is protected by a protection layer 14.
The width for the upper magnetic pole front end layer 8 on the air bearing surface 15 is formed in a width corresponding to a track width. The conductor coils 12, 12′ are constituted so as to surround the rear end 16 of the upper magnetic pole upper layer. Application of a recording current to the conductor coils 12, 12′ induces magnetic fluxes in the upper magnetic pole upper layer 13, the upper magnetic pole rear end layer 9 and the lower magnetic pole 5 and records signals in a recording medium 17 that runs spaced apart by a minute distance from the air bearing surface 15 by recording magnetic fields generated from the front end of the recording gap. Magnetic fluxes are concentrated from the lower magnetic pole 5 in the vicinity of the recording gap to generate high recording magnetic fields. The length in which the upper magnetic front end layer 8 is in contact with the recording gap layer 6 is referred to as a gap depth Gd, and the recording magnetic fields increase as the gap depth decreases since the magnetic fluxes are concentrated to the magnetic pole gap end.
Further, as a method of improving the accuracy upon forming the narrow track, a recording/reproducing separated type thin film magnetic head shown in FIG. 4 is proposed in Patent Document 2. For the head proposed, a lower magnetic pole front end layer 19 and a lower magnetic pole rear end layer 20 are disposed on a lower magnetic pole main layer 18 and a gap therebetween is filled and planarized with a lower non-magnetic insulating layer 21, to form a recording gap layer 6, and then a resist frame is prepared on the planar surface to form an upper magnetic pole front end layer 8. Thus, a narrow track width can be formed with high accuracy.
FIG. 5 shows a perspective view for the head front end of the recording/reproducing separated type thin film magnetic field shown in FIG. 4. In both of the thin film magnetic head shown in FIG. 3 and FIG. 4, a trimmed portion 22 having a width substantially equal to a track width Tw is formed at the front end of the lower magnetic pole 5 and the lower magnetic pole front end layer 18, thereby decreasing so-called fringe magnetic fields that leak to the outside of the track width Tw.
Patent Document 1
Japanese Published Application 2000-276707 (pages 7–8, FIG. 2)
Patent Document 2
Japanese Published Application 2002-157705 (page 3, FIGS. 1–2)
In the prior art described above, the lower magnetic pole 5 or the lower magnetic pole front end layer 19 is subjected to ion milling or reactive ion etching using the track forming portion of the magnetic pole front end layer 8 as a mask to form the trimmed portion 22. Accordingly, the height Tr for the trimmed portion 22 is limited to about 2 to 3 times the recording gap and it is extremely difficult to increase the height of the trimmed portion 22 in view of manufacture. Therefore, it is difficult to effectively decrease the magnetic fields that leak to the outside of the track width to possibly record surplus signals on adjacent tracks or gradually erase recorded signals in the adjacent tracks due to a great number of times of recording operations along with decrease in the track pitch.